Generally widespread digital cameras employs, as a recording medium for images taken, a memory built in the cameras or a memory card removable from the cameras. Various types of memory cards are released and available.
Meanwhile, for a recording and playback device, such as a DVD recorder, that records and plays back a broadcast program, a model has been introduced that has a card slot for loading a memory card and has functions of copying image files (including still image files and moving image files) stored in the memory card to a mass recording medium (for example, hard disk drive) in the device and storing the image files, playing back the stored image files, and displaying the image files on a screen of a television set connected to the recording and playback device with a video signal cable.
The introduction of the above-described recording and playback device allows a user to easily play back and display the image files on a big screen of a television set and enjoy it, as long as the files shot with a digital camera are stored in the recording and playback device.
In copying image files to the mass recording medium in the above-described recording and playback device, it is generally done by a user to provide a preview of image files which are copy targets on a television screen, and select an image file(s) after confirming images.
However, a selection operation by a preview display is performed by a remote control operation of the recording and playback device, and thus the selection operation is a quite burdensome operation for the user, which is in turn a cause of preventing easy operation for copy to the recording and playback device.
As a copy scheme for solving such a problem, a method of copying all image files in a memory card to a mass recording medium of a recording and playback device has been introduced (hereinafter, referred to as the “medium batch copy scheme”).
In the medium batch copy scheme, since the user does not need to select an image file(s), a copy can be easily performed to the mass recording medium of the recording and playback device. However, the batch copy scheme has the following problem.
Specifically, after copying still image files or moving image files recorded in the memory card to the mass recording medium of the recording and playback device, if a batch copy is performed again with the still image files and moving image files that have been copied remaining without being deleted from the memory card, then the still image files or the moving image files that have already been copied are copied again and thus such still image files or moving image files are stored in the mass recording medium redundantly.
Here, with an increase in the storage capacity of the memory card, the case in which image files remain in the memory card without being deleted therefrom is increasing. Accordingly, in the batch copy scheme, the number of image files to be stored redundantly is increasing. The occurrence of duplicative storage not only wastefully squeezes the storage capacity of the mass recording medium of the recording and playback device but also causes a plurality of the same files to be present on the same mass recording medium, which becomes a big cause of a reduction in file search efficiency upon playback.
Conventionally, in order to circumvent such inconveniences, various techniques have been proposed. For example, in Patent Document 1, a memory card that is used for receiving/sending image files from/to a digital camera is assigned a unique medium ID code which is assigned to each memory card and different in each memory card, and the unique medium ID code together with a time stamp and a data size are written in an image file as identification information. Then, upon copy to the mass recording medium of the recording and playback device, identity between image files on the recording and playback device and image files in the memory card is judged using the identification information, and then it is judged whether the image files have been copied. For copied files, a copy is skipped, and duplicative storage is prevented.
A copy as described above which is a batch copy of only image files that have not been copied yet after determining whether image files have already been copied to a copy destination device is hereinafter referred to as a “differential copy”.
In the above-described conventional case, before copying image files stored in the memory card, identity check is made for all image files between the mass recording medium of the recording and playback device and the memory card to determine whether the image files have not been copied yet. And only image files that are determined to have not been copied yet are copied to and stored on the mass recording medium, and thus duplicative storage can be prevented. In addition, since a unique medium ID which is uniquely assigned to each memory card is used in the identity check, erroneously-determining and duplicative storage can be prevented even in the case that a plurality of memory cards are used.    Patent Document 1: JP-A-2004-341630